In internal combustion engines, fuel and air may be introduced into cylinders for combustion. Pistons may move within the cylinders under the influence of a crankshaft located in a crankcase. In each cylinder, a piston may compress the fuel and air mixture preparatory to combustion of the mixture. Combustion may then drive the pistons and yield power output. The power output may be used to drive a machine. Along with the desired output of power, combustion products are created. Most of these combustion products are exhausted from the cylinder into an exhaust system.
The seal or fit between pistons and cylinders is not perfect. Some of the combustion products may blow by the pistons and enter into the crankcase. These combustion products are termed “blow-by gases” or “blow-by.” Blow-by gases contain contaminants normally found in exhaust gases, such as, for example, hydrocarbons (HC), carbon monoxide (CO), NOx, soot, and unburned or partially burned fuel. Lubricating oil in the crankcase tends to be atomized or otherwise entrained in the hot blow-by gases to form what may be termed an aerosol.
Blow-by gases in the crankcase, including entrained lubricating oil, must be vented as crankcase emissions to relieve pressure in the crankcase. Some systems vent the crankcase emissions directly to the atmosphere. Such venting may place undesirable portions of crankcase emissions directly into the environment. Other systems direct the crankcase emissions into the engine exhaust system where they receive emission treatment to the same extent engine exhaust gases receive treatment before release to the environment. Still others direct the crankcase emissions either to the air intake side of the engine for mixing with the air and fuel introduced into the cylinders, or to the engine exhaust system where they are treated and recirculated for introduction into the air intake system. Those systems where the crankcase emissions are reintroduced into the engine for burning belong to the class of closed crankcase ventilation (CCV) systems.
Some engines, such as large diesel engines, for example, utilize forced induction to enhance the power output of the engine. This may involve superchargers or turbochargers. Returning crankcase emissions to the intake side of a compressor in a supercharger or turbocharger can result in fouling of the compressor wheel in a relatively short time period. The fouling is compounded in multiple turbocharger systems as the heat increases in downstream compressor units. Additionally, cooling units downstream of a supercharger or turbocharger may be fouled. Therefore, crankcase emissions must undergo extensive purification before being returned to the intake in a supercharged or turbocharged engine. Further, even with extensive purification, some level of contamination may still exist that may be harmful to the supercharger or turbocharger, cooling units, or various engine components.
Some machines deriving power from internal combustion engines also have various components or systems that utilize compressed air for their operation. For example, a machine may be provided with an air operated braking system requiring compressed air for its operation. A machine may also be provided with various air operated actuators requiring compressed air for operation. In addition, it may sometimes be necessary to provide some type of pumping unit to assist in venting blow-by gases and resulting crankcase emissions from the crankcase of the engine of the machine.
An internal combustion engine may operate over a range of speed and load conditions. Over this range of speed and load conditions, blow-by gases and resulting crankcase emissions may vary substantially. Blow-by gases and resulting crankcase emissions may likewise vary over the life of an engine as relevant parts encounter wear and tear from use. Variations in blow-by gases and crankcase emissions may cause significant fluid flow variations in venting the crankcase emissions. Some control over these resulting fluid flow variations, for example by suitable valving, may be beneficial and desirable.
A crankcase ventilation system is disclosed in U.S. Pat. No. 6,892,715, issued to Norrick on May 17, 2005. In the system of the Norrick patent, the crankcase emissions are passed to a compressor which in turn delivers the crankcase emissions directly into the engine air intake system. A bleed air line is provided to supply air to the compressor when crankcase emissions are not sufficient to satisfy compressor demands. Upstream of the compressor and downstream of the air bleed line, an oil separator is provided to separate oil from the crankcase emissions. Downstream of the oil separator and upstream of the compressor, a relief valve is provided for those situations where crankcase emissions exceed compressor intake demands.
While the system of Norrick may be successful in removing oil from the crankcase emissions to some extent and delivering crankcase emissions into the engine air intake system, the compressor is dedicated solely to delivering the crankcase emissions, and any air drawn in through the bleed air line, to the air intake system. The efficiency of dual use of the compressor is lacking since the compressed fluid exiting the compressor is not available for components which use compressed air for their operation. Moreover, the only treatment of the crankcase emissions prior to being injected into the air intake system is oil separation. Products of combustion present in the crankcase emissions are left untreated and allowed to directly enter the engine intake where they may cause engine damage.
The disclosed closed crankcase ventilation system is directed toward improvements and advancements over the foregoing technology.